SIGIRR and neoplasm: The presence and absence of IL-1R8 expression in tumors from MMTV-neu/IL-1R8+/+ and MMTV-neu/IL-1R8−/− mice, respectively, were confirmed by immunohistochemistry (IHC) and, in tumors from MMTV-neu/IL-1R8+/+ animals, IL-1R8 expression was predominantly detected in the tumor cells (Figure 2A).